1. Field of the Invention
The present invention relates to a four-way reversing valve which is one of direction control valves to control the direction of flow of liquid in a hydraulic or pneumatic circuit and is used, for example, to change the flow of coolant when a cooling or heating operation is selected in a heat pump air conditioning system for a double use of cooling and heating, and particularly, is configured as a solenoid hydraulic operating type using an inner pilot method by incorporating a solenoid-controlled pilot-operated valve and a vane type spool valve which is operated by pilot hydraulic pressure of the solenoid-controlled pilot-operated valve.
2. Description of the Related Art
A heat pump air conditioning system for a double use of cooling and heating uses a heat transfer mechanism performed during a cycle formed of compression, condensation, expansion, and evaporation of coolant and generates cold or hot air flow needed for cooling or heating through heat exchange between the condensation and evaporation steps. Theoretically, the cooling operation or heating operation in such a system could be selected by switching the position of heat exchangers (a condenser and an evaporator) used in the condensation and evaporation steps, respectively. However, switching the positions of the condenser and the evaporator is practically impossible. Thus, the flow of coolant with respect to the condenser and evaporator is changed by using a four-way reversing valve that is one of direction control valves.
A conventional four-way reversing valve used for the cooling/heating operation of a heat pump air conditioning system for a double use of cooling and heating, as shown in FIG. 1, is an inner pilot type four-port two-position solenoid-hydraulic operated direction control valve combined with a main valve 10 and a pilot valve 20. The main valve 10 has four ports and two pilot connection holes located at both left and right ends of the main valve 10. Four coolant connection pipes 11, 12, 13, and 14 connected to an outlet and an inlet of a compressor and coolant pipes of indoor and outdoor heat exchangers of an air conditioning system are welded at the main valve 10. Also, the pilot valve 20 is combined with the main valve 10 into an inner pilot type through four capillary pipes 21, 22, 23, and 24. Reference numeral 27 denotes a solenoid coil for controlling the pilot valve 20.
FIGS. 2A and 2B show the conventional four-way reversing valve together with an air conditioning system circuit. Referring to the drawings, the pilot valve 20 combined with the main valve 10 is a four-port two-position spring offset solenoid operated type. A pilot spool 25 is moved to a normal position by a spring 26 and a converting position by an electromagnetic force obtained by exciting the solenoid coil 27 so that one of load ports A and B of the pilot valve 20 is connected to a supply port P while the remaining load port is connected to a drain port R. The exciting current of the solenoid coil 27 is blocked when a cooling operation of an air conditioning system is selected. After a heating operation is selected, the exciting current of the solenoid coil 27 is continuously applied during the operation.
That is, when the cooling operation is selected, the pilot spool 25 is positioned at the normal position as shown in FIG. 2A. Here, pilot pressure in a chamber 15 at one side of the main valve 10 is higher than the other side of the main valve 10. Then, a main spool 17 of the main valve 10 is moved to the left and a supply port P of the main valve 10 is connected to a load port A thereof. A load port B of the main valve 10 is connected to a drain port R thereof. Thus, in the air conditioning system, coolant exhausted from an outlet of a compressor 1 is transferred to an outdoor heat exchanger 2 through the ports P and A of the main valve 10 so that the outdoor heat exchanger 2 works as a condenser. The coolant depressurized by an expansion mechanism 3 is transferred to the indoor heat exchanger 4 so that the indoor heat exchanger 4 works as an evaporator. The coolant is transferred from the indoor heat exchanger 4 to an inlet of the compressor 1 through the port B and R of the main valve 10, thus a cooling cycle is carried out.
Next, when a heating operation is selected, the pilot spool 25 is moved to a converting position by the solenoid coil 27, as shown in FIG. 2B. Here, pilot pressure in a chamber 16 at the other side of the main valve 10 is higher than the chamber 15. Then, the main spool 17 of the main valve 10 is moved to the right and the supply port P is connected to the load port B. The load port A at the other side of the load is connected to the drain port R. Thus, in the air conditioning system, the coolant exhausted from the outlet of the compressor 1 is transferred to the indoor heat exchanger 4 through the ports P and B of the main valve 10 so that the indoor heat exchanger 4 works as a condenser. The coolant depressurized by the expansion mechanism 3 is transferred to the outdoor heat exchanger 2 so that the outdoor heat exchanger 2 works as an evaporator. The coolant is transferred from the outdoor heat exchanger 2 to the inlet of the compressor 1 through the port A and R of the main valve 10, thus a heating cycle is carried out.
In the meantime, Korean Registration Utility Model Publication Nos. 0127597, 0130152, and 20-0213450 and Korean Patent Publication No. 2001-0007231 disclose various types of main valve operating means in which a slide type spool of the main valve is directly converted by using a thermodynamic piston mechanism, instead of the above-descried pilot valve, or a rotary spool driven by an electric motor is provided at the main valve.
However, the thermodynamic piston mechanism or electric motor for directly driving the main spool is hardly used because converting time is slow and converting operation is inaccurate, and thus the use of such devices results in malfunctions in the operating system.
As a valve used in a hydraulic or pneumatic circuit, a solenoid operated type valve such as the above-described pilot valve is widely used due to its merits of easy control of automatic operation or remote operation and fast and accurate converting time. However, since the solenoid operated type valve utilizes electrical thrust of a solenoid, it is not appropriate for a case of controlling a huge amount of fluid and is usually used for conversion at a pressure of 210 kg/cm2 and the maximum fluid amount of 80 l/min. Accordingly, the conventional four-way reversing valve as described above is generally configured such that the main valve is a hydraulic operating type and the pilot valve operating the main valve is a solenoid operated type.
To manufacture a four-way reversing valve formed by combining the main valve and the pilot valve, capillary pipes whose diameters are small are further provided, in addition to the coolant connection pipes welded at the main valve. Thus, the number of welding points increases so that manufacturing of a four-way reversing valve becomes complicated and breakdown during manufacture and use thereof is frequent due to welding defects.
To solve the above-described problems, it is an object of the present invention to a four-way reversing valve which is a solenoid operated type exhibiting an easy control and fast and accurate converting time, in which pilot pressure is converted and a vane type main spool is rotated by using the converted pilot pressure, so that the number of welding points are minimized.
To achieve the above object, there is provided a four-way reversing valve which comprises a valve casing having a plurality of ports through which fluid flows, a valve main body fixedly installed to the valve casing and having a valve chamber in which a plurality of main port connection holes for selectively connecting the ports are formed, a main spool rotatably installed at the valve chamber of the valve main body, for selectively connecting the ports according to a rotation position, and a spool driving unit for reversibly rotating the main spool by using part of fluid supplied through one of the ports in the valve casing.
It is preferred in the present invention that the ports of the valve casing comprise a supply port for connecting to a fluid supply source, two load ports for connecting to an external load, and a drain port for draining, the main spool comprises a spool portion for selecting one of the two load ports and a groove passing through the spool portion and connected to the drain port, and the four way reversing valve operates by forming a first main flow path for moving fluid from the supply port to one of the two load ports via the valve chamber, and a second main flow path for moving fluid from the other one of the two load ports to the drain port via the groove.
It is preferred in the present invention that the valve main body further comprises a pilot hydraulic chamber which is formed by extending one side of the valve chamber and has two pilot input and output ports penetrating the pilot hydraulic chamber to alternately input and output the part of fluid in two opposite directions inside the valve casing and a pilot drain port for obtaining a pilot hydraulic pressure, that the main spool further comprises a vane portion formed by extending one side of the main spool to be rotatable between the two pilot input and output ports in the pilot hydraulic chamber, and that the spool driving unit can select one of the two pilot input and output ports.
It is preferred in the present invention that the spool driving unit comprises a solenoid for generating an electrical thrust by being excited by an electric signal, a plunger moved by the electrical thrust of the solenoid, a spring developing an elastic force to return the plunger in an opposite direction to the electrical thrust, and a pilot spool coupled to the plunger, and moving and returning together with the plunger and having a cavity for connecting one of the two pilot input and output ports and the drain port.
According to the present invention, since the main spool is directly rotated by applying pilot hydraulic pressure in the valve main body, the additional capillary pipe needs not be welded unlike the conventional technology.